1. Field of the Invention
The present invention relates to a photographic film support and, more particularly, to a support for photographic films which has been treated so as to prevent halation and light piping (edge fog).
2. Description of the Prior Art
In general, supports for motion picture or recording films should be treated so that halation and light piping does not occur. If such are not prevented, disadvantages occur. For example, when one frame is exposed to light with a camera, (1) incident light scatters in the support or at the interface between the support and a subbing layer to cause formation of dim images due to the undesired exposure of the emulsion in that frame; and (2) incident light which passes through the support reaches another exposed or unexposed frame and the emulsion of the frame is fogged.
In the past, photographic supports have been dyed to prevent halation and light piping.
For instance, as disclosed in Japanese patent application (OPI) Nos. 14245/72 and 5425/73 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application"), U.S. Pat. Nos. 2,622,026, 3,728,124 and 3,822,132, etc., it is known to dye a photographic film support with red and green dyes. Further, as disclosed in U.S. Pat. No. 3,340,062, a support for a photographic film in which finely divided powders of pigments such as a carbon black, titanium oxide, etc., is also known.
In general, light which causes halation and light piping is visible light, such as sunlight, etc. For this reason, it would appear that, if a support for a photographic film were dyed so as to have an absorption over the entire spectral wavelength range of visible light, halation and light piping could be prevented. Thus, supports for photographic films dyed to have a uniform absorption in the entire visible light wavelength range of about 400 to 700 nm are described in U.S. Pat. No. 2,622,026, column 1, lines 16 to 20.
Where a support for a photographic film is dyed with a dye mixture of a red dye (which has a main absorption peak in the wavelength range of 500 to 600 nm) and a green dye (which has main absorption peaks in the wavelength range of 400 to 500 nm and of 600 to 700 nm, respectively) to thereby prevent halation or light piping, there is the disadvantage that sufficient halation preventing effect or light piping preventing effect is not obtained or the apparent sensitivity of the photographic emulsion is decreased. Green dyes have main absorption peaks in the wavelength ranges of 400 and 500 nm and 600 and 700 nm. The main absorption peaks in these two wavelengths ranges result in an optical density which is generally not the same, namely, the main absorption peak in one range results in an optical density which is higher than the optical density resulting from the main absorption peak in the other range. For this reasin, green dyes do not possess the same optical densities in the wavelength range of from 400 to 500 nm and in the wavelength range of from 600 to 700 nm. Therefore, sufficient prevention of halation or prevention of light piping is not obtained in the wavelength range having the smaller optical density. In addition, although sufficient prevention of halation or prevention of light piping can be achieved by increasing the concentration of the green dye, if the concentration of the green dye is increased, a disadvantage that the incident light at the wavelength range having a larger optical density is absorbed in the support to cause a reduction in the apparent sensitivity of the emulsion which is sensitive to this wavelength range occurs.
In addition, the method for incorporating pigments such as finely divided titanium oxide, carbon black, etc., involves the disadvantage that uniform dispersion of these pigments in the support polymer is difficult to achieve and, furthermore, an increase in the haze degree (haze of a support) as a support for a photographic film occurs, thus, clear images are not obtained.
By using three kinds of dyes comprising a yellow dye, a red dye and a blue dye and by suitably selecting the dye mixing ratio, a support for a photographic film in which the optical densities of each of the main absorption peaks in the wavelength regions of 400 to 500 nm, 500 to 600 nm and 600 to 700 nm is the same can be obtained and, as a result, the decrease in sensitivity of the photographic light-sensitive material is minimized and sufficient prevention of halation and prevention of light piping is obtained. In addition, by changing the mixing ratio of the three dyes, it is possible to correct the color balance even in a color emulsion having poor color balance.
Dyes for dyeing polyester films for use as a support for photographic films must be simultaneously heat resistant, compatible and sublimation resistant, must be inert to silver halide emulsions, and must not adversely affect the photographic properties such as sensitivity, gamma, fog, etc.
Red and blue dyes which meet these requirements are those as described in Japanese patent application (OPI) Nos. 14245/72 and 5425/73, Japanese patent publication Nos. 8734/72, 8735/72 and 33724/76, U.S. Pat. Nos. 3,728,124, 3,822,132, and 3,933,502, etc. However, few yellow dyes which meet the requirements described above are known, and it has been desired to develop yellow dyes which are heat resistant, compatible with polyesters and sublimation resistant, which are inert to silver halide emulsions and which do not adversely affect the photographic properties such as sensitivity, gamma, fog, etc.